The Cardiovascular System

The Heart, Blood Vessels, Blood Types

The Closed Circulatory System•Humans have a closed circulatory system, typical of all vertebrates, in which blood is confined to vessels and is distinct from the interstit ial f luid.

–The heart pumps blood into large vessels that branch into smaller ones leading into the organs.

–Materials are exchanged by dif fusion between the blood and the interstit ial f luid bathing the cells.

The HEART

The Heart - cardiac muscle t issue–highly interconnected cells–four chambers

•Right atr ium•Right ventricle•Left atr ium•Left ventricle

Functions of the Heart

• Generating blood pressure• Routing blood

– Heart separates pulmonary and systemic circulations

• Ensuring one-way blood flow– Heart valves ensure one-way f low

• Regulating blood supply– Changes in contraction rate and force

match blood delivery to changing metabolic needs

Figure 15.3a

Figure 15.3c

Chambers

• 4 chambers• 2 upper chambers= Atria

– Between is interatrial septum– Contains fossa ovalis- remnant of foramen

ovalis

• 2 lower chambers = ventricles– Between is interventricular septum

• Wall thickness depends on work load– Atria thinnest– Right ventricle pumps to lungs & thinner

than left

Blood Flow Through Heart

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Conduction System of the Heart – Sinoatrial (SA) Node

• Heartbeat is init iated by the cardiac muscle fibers of the sinoatrial (SA) node. – located in the posterior wall of the right atr ium,

adjacent to the entrance of the superior vena cava

• Act as the pacemaker.– rhythmic center that establishes the pace for

cardiac activity • Init iates impulses 70 - 80 times per minute. • STETHOSCOPE – instrument that hears

the heartbeat (lub-dub)

Circulations•Pulmonary circuit–responsible for carrying deoxygenated blood from the right side of the heart to the lungs, and then returning the newly oxygenated blood to the left side of the heart.

•systemic circuit - responsible for carrying oxygenated blood from the left side of the heart to the dif ferent parts of the body.

Figure 15.4ab

Figure 15.4d

The BLOOD VESSELSA network of tubes

–Arteriesarterioles move away from the heart•Contains oxygenated blood (except the pulmonary artery)

–Capil laries – where gas exchange takes place.

–VeinsVenules moves towards the heart•Skeletal Muscles contract to force blood back from legs•One way values•When they break - varicose veins form•Contains deoxygenated blood (except the

aorta)

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The BLOOD

• Considered a connective t issue: contains– Cells– a l iquid ground substance (called plasma)– dissolved protein f ibers.

• About four t imes more viscous (or thicker) than water.

• Temperature of blood is about 1°C higher than measured body temperature.

Functions

• Transportation-hormones, gases, nutrients, ions, heat

• Regulation- pH, temperature, water balance in cells

• Protection- clott ing, white cells interferons, complement

Composition

• Connective tissue-Two parts– Plasma = soluble materials (~55%)– Formed Elements = cells (~45%)

• Percent occupied by red blood cells (RBC) = hematocrit (Hct)

• White blood cells (WBC) ~1%

A. Plasma

Liquid port ion of the blood. Contains clott ing factors, hormones, antibodies, dissolved gases, nutrients and waste

B. Erythrocytes - Red Blood Cells

–Carry hemoglobin and oxygen. Do not have a nucleus and l ive only about 120 days.

–Can not repair themselves.

C. Leukocytes – White Blood cells

–Fight infection and are formed in the bone marrow

–Five types – neutrophils, lymphocytes, eosinophils, basophils, and monocytes.

•D. Thrombocytes – Platelets.

–These are cell fragment that are formed in the bone marrow from magakaryocytes .

–Clot Blood by st icking together – via protein f ibers called f ibrin.

Blood Types

• Surface antigens- react with antibodies

• Two antigens = A & B• If have only A –type A• If have only B –type B• If neither then Type O

• Blood usually has antibodies that can react with antigens– e.g. anti-A antibody or anti-B antibody

• You don’t react with your own antigens– Thus: type A has anti-B and vice versa

Transfusions

• If mismatched blood given antibodies bind to it and hemolyze cells

• Type AB has no AB antibodies so can receive any ABO type blood called Universal recipients

• Type O have neither antigen so can donate to any other ABO type called Universal donors

Figure 14.6

Rh Blood Group

• Antigen discovered in rhesus monkey• If have antigen- Rh +

• Normally don’t have antibodies• antibodies develop after the f irst

exposure from transfusion

Checking Circulation- Pulse

• Pulse in arteries = HR– Use radial artery at wrist, – carotid artery, – brachial artery

• Tachycardia = rapid rest rate (>100 bpm)

• Bradycardia= slow rest rate (<50 bpm)

Blood Pressure

• Use sphygmomanometer – Usually on brachial artery

• Raise pressure above systolic- – stop f low

• Lower pressure in cuff unti l f low just starts– first sound Systolic Pressure

• Lower unti l sound suddenly gets faint Diastolic pressure

• Normal values <120 mmHg for systolic & < 80 mmHg for diastolic

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Blood Pressure

• Force/unit area blood places on the inside wall of a blood vessel.

• Measures in mmHg• Sphygmomanometer: device to

measure blood pressure. • Systolic blood pressure

(contraction)• Diastolic blood pressure

(relaxation)• 120/80 mmHg

Disorders of the Cardiovascular System• Anemia - lack of iron in the blood, low RBC count

• Leukemia - white blood cells proliferate wildly, causing anemia

• Hemophil ia - bleeder’s disease, due to lack of f ibrinogen in thrombocytes

• Heart Murmur - abnormal heart beat, caused by valve problems

• Heart attack - blood vessels around the heart become blocked with plaque, also called myocardial infarction

Effects of Aging on the Heart

• Gradual changes in heart function, minor under resting condit ion, more signif icant during exercise

• Hypertrophy of left ventricle• Maximum heart rate decreases• Increased tendency for valves to

function abnormally and arrhythmias to occur

• Increased oxygen consumption required to pump same amount of blood

Stiffening of the aorta

Atherosclerosis

Arterosclerosis

Aerobic exercise ( longer than 20 mins) strengthens cardiovascular system